This invention relates to input coupling apparatus and, more particularly, to a universal input coupling device which finds particular utility in the environment of a telecommunications logger to permit signals received over different types of telephone lines or external communications links (e. g. a radio link) to be recorded. As will become apparent from the description below and from the appended claims, the present invention is not intended to be limited solely to the field of telecommunications loggers.
In various applications, it is desired to receive audio or other information signals from divers sources and over different types of telecommunications links. For example, such audio or other information signals may be recorded, may be relayed, may be broadcasted or may be otherwise processed. In one particular application, such audio signals are recorded for verification, confirmation or other purposes at a time subsequent to the recording thereof. So-called communications recorders, also known as telecommunications loggers, comprise one type of such audio devices.
As is known, a conventional telecommunications logger (sometimes referred to hereinafter simply as a "logger") is comprised of a multi-channel audio recording device, in which individual recording channels are coupled to respective tracks on a magnetic recording medium, such as a magnetic tape, for the recording of audio signals. Several, and even all, of these recording channels may be "active" simultaneously to record individual conversations in respective recording tracks. On the other hand, as few as one single recording channel may be active at any given time. The magnetic medium may be advanced when any one or more channels is active and stopped only when all input channels are inactive. In other applications, the medium is continuously advanced twenty-four hours each day.
A typical use of a conventional telecommunications logger is to record emergency information that may be communicated to, for example, a police station, a fire station, a medical emergency unit, or the like. In such an environment, each recording channel may be coupled to a respective telecommunications link to receive and record audio (or other information) signals communicated over that link. For example, several recording channels may be connected to respective ones of many incoming telephone lines provided at the recording station (e. g. incoming telephone lines at a police station). In the likely event that emergency information is communicated over other communications links, such as a radio link, a dedicated hard-wired line, or the like, such additional communication links also are coupled to respective recording channels.
When a police department, as an example, acquires a telecommunications logger, the particular recording channels which are to be connected to telephone lines and those which are to be connected to other communications links normally are specified in advance of installation. When the logger initially is set up and configured at the police station, the specific recording channels that are to be connected to the telephone lines and to the other communication links then are identified. Often, on-site changes must be made quickly to accommodate changes in plans, configurations and intended uses of the logger. Often, this requires the particular expertise of highly skilled technicians and, as is apparent, is significantly labor intensive.
An essential element in the operation of a typical telecommunications logger is that an incoming audio signal is recorded automatically and without manual initiation by an operator. This ensures that emergency information is recorded quickly, promptly and accurately. Most emergency information is received in response to incomming telephone calls or radio transmission initiated at a remote location. It is important, then, that an incoming telephone call be answered automatically and that the resultant off-hook condition of a telephone line which has been answered be detected. However, the detection of such off-hook conditions generally varies as a function of the type of telephone system then in use.
For example, in one type of telephone system, an off-hook condition (i. e. the "answering" of an incoming telephone call) is accompanied by a change in the voltage level at the usual tip and ring leads of a telephone line. While this change in tip and/or ring voltage may be detected without difficulty, it often happens that the off-hook voltage levels used in one telephone system differ from those used in another. For this reason, an off-hook condition often is detected by sensing current flow in the telephone line. However, current sensing circuitry, although conventional, usually is connected in series with the tip and/or the ring lead; and this generally requires the leads to be spliced for insertion of the current sensing circuit. Such telephone line splicing may be an accommodation furnished by the telephone utility which, in turn, provides the usual tip and ring leads, and additional "ring 1" and "tip 1" leads. In the example described below, the tip and tip 1 leads are shorted together, and the ring and ring 1 leads are connected in series; and the current sensing circuit is connected between the ring and ring 1 leads.
Still further, if the recording channel of the logger is to be connected to another communications link, such as a radio link, the radio communications device may be provided with a pair of terminals that provide the audio signals analogous to those present on the tip and ring leads of a telephone line, together with another terminal upon which a simulated off-hook signal generally is known as a "remote start" signal which, when present, indicates the presence of audio signals to be recorded.
The signal levels on different telephone lines may vary in intensity, usually as a function of the length of the telephone line which extends to the logger. In some locations, the signal strength associated with all of the telephone and other communication lines may be relatively high; whereas in other locations, those signals strengths may be relatively low. Still further, in any given location, the signal strengths on some lines may exceed the signal strengths on others. To compensate for these different signal levels, different signal gains or attenuations may be needed for the different recording channels. As is apparent, such "normalization" of signal levels may vary from one logger to another and even from one recording channel to another in the same logger.
Heretofore, each recording channel in a logger, or each input interface to that recording channel, has been "customized" to accommodate the different conditions expected in that channel. Thus, if a particular channel was connected to a telephone line, either a voltage sensing circuit or a current sensing circuit would be provided in the input interface. If that particular channel was to be connected to another communications link, such as a radio device, then a "remote start" sensor would be provided in the input interface. Still further, if the level of the audio signal supplied to the recording channel is relatively high, then the input interface would be provided with an attenuator of proper attenuation level. This attenuation level might vary from one recording channel to another. In any event, it is appreciated that the particular configuration of the various input interfaces in a logger has been quite time-consuming and expensive. Furthermore, if servicing had been required for that logger, the specific configuration of the different input interfaces would have to be known and accounted for.
The present invention overcomes the aforenoted difficulties.